The present invention relates to an endoscopic flexible tube serving as a sheath for the insertion portion or other parts of an endoscope.
Endoscopic flexible tubes generally comprise a helical tube, a reticulate tube covering the outer surface of the helical tube, and a jacket covering the outer surface of the reticulate tube. The helical tube is formed of a metal or plastic strip wound spirally in a specified diameter. The reticulate tube is formed of braided thin metal wires. The jacket is made of a synthetic resin material.
The jacket commonly has a simple single-layered structure but it is by no means rare that a plurality of layers are superposed to provide a xe2x80x9cmulti-layered structurexe2x80x9d that adds several improvements on the flexible tube such as greater ease with which it can be inserted into a body cavity and higher chemical resistance.
A problem with the jacket having a multi-layered structure is that the individual layers must be securely bonded to insure that they will not separate from each other even if the jacket is subjected to repeated bends during service.
This not only adds to the time and manpower required by the overall manufacturing process; due, for example, to uneven coating of adhesives, the adhesion between layers in the multi-layered structure portion may become locally insufficient or the adhesives may deteriorate with time to cause separation of adjacent layers.
An object, therefore, of the invention is to provide an endoscopic flexible tube that allows for easy fabrication of a jacket of a multi-layered structure that is adequately protected against separation of overlying layers.
According to the invention, two overlapping layers in a multi-layered structure portion of a jacket of an endoscopic flexible tube are integrally combined via an area that comprises a mixture of the constituent materials of said two layers. The constituent materials of said two layers are preferably mixed together in a molten state to form the mixture. Because of this structure, the jacket is resistant to separation between overlapping layers.
In a preferred embodiment, an endoscopic flexible tube comprises a helical tube formed of a strip wound in turns of a coil that are spaced by gaps in the pitch direction, a reticulate tube that is covered on the surface of said helical tube and which is formed of reticulately braided bundles of wires, and a flexible jacket that is coated on the outer surface of said reticulate tube and at least part of which has a multi-layered structure comprising a plurality of superposed layers, wherein two overlapping layers in the multi-layered structure portion of said jacket are integrally combined via an area that comprises a mixture of the constituent materials of said two layers.
If desired, the inner layer of the multi-layered structure portion of said jacket may be made of a soft synthetic resin material and the outer layer of a harder material having high chemical resistance.
In another embodiment, either the inner layer or the outer layer or both the inner and outer layers of the multi-layered structure portion of said jacket may have a plurality of portions with different characteristics along the longitudinal axis of said endoscopic flexible tube, with adjacent ones of said portions being integrally combined via an area that comprises a mixture of the constituent materials of said two adjacent portions.
The mixture area in the multi-layered structure portion of said jacket may be such that it was formed of the constituent materials on the opposite sides that intermingled when they were molten simultaneously. If desired, the inner layer of the multi-layered structure portion of said jacket may protrude inward of said reticulate tube through the mesh openings therein.
The present disclosure relates to the subject matter contained in Japanese patent application No. Hei. 11-119286 (filed on Apr. 27, 1999), which is expressly incorporated herein by reference in its entirety.